Method of cutting gears



Sept. 19, 1944. L. o. CARLSEN 2,358,442

METHOD OF CUTTING GEARS Original Filed Aug. 1, 1941 2 Sheets-Sheet 1 Z6 7 I 38 Y I l 3 4 i 25 45 a 4 v d \56 4: I

- I nvvslvrfok LEONARD 0. CHELSEA/- TORNEY Sept. 19,'1944.- L. o. CARLSEN 2,358,442 7 METHOD OF CUTTING GEARS Original Filed Aug. 1, 1941 2 Sheets-Sheet 2 INVENTOR LEONARD 0. cfiRLsE/v Patented Sept. 19, 1944 235 ,4442 METHOD OF CUTTING GEARS I I Leonard OQCarlsen, Rochester, N. Y., assignor to Gleason Works, I of New York Rochester, N. Y., a corporation Original application August 1, '1941, Serial No. 405,064. Divided and this application July 20,

1942, Serial No. 451,536

8 Claims. (01:90-45) The present invention relates to. a method of and to a tool for cutting gearsand particularly to a method of andtool for cutting fine-pitch straight bevel gears. I

Considerable metal has to be removed from the interdental spaces o'f'gears of coarse pitch in order to produce the final finished tooth form.

It is the practice, therefore, to cutsuch gears in two steps, first rough-cutting. the gears to approximate shape "and then finishing-cutting them. In very fine-pitch jobs, however, the amount of metal, that has to be removed in order-to form the tooth spaces, is quite small. For reasons of economy, then, such gears may be cut from the solid in one operation without any preliminary roughing-cut. With the tools and-cutting methods heretofore employed, how

ever, it has been difiicult in a single cut or socalled completing operation to obtain an entirely. smooth tooth surface finish, for the cutting edges, which'rough out the tooth space, have also to finish the tooth sides.- Furthermore, in the completing method, the' tooth spacing sometimes does not have the required accuracy because the cutting thrusts are diiferent on the two tools which cut the opposite sides of the 'teeth.- Hence, Where the requirements of finish and accuracy are high, it has been the practice heretofore to take separate roughing and finishing cuts on fine pitch jobs as well as on coarse pitch jobs.

One'object of the present invention is to provide a method whereby gears and particularly fine pitch gears may be cut from the solid in one operation with extreme accuracy and smooth tooth surface finish.

A further object of the invention is to provide a method for cutting gears from the solid in one operation with which separate roughing and finishing cuts may, nevertheless, be taken successively on the sides of the gear teeth.

Still another object of the invention is to provide a method for cutting gears from the solid in one operation in which separate roughing and finishing cuts may be taken successively without any appreciable increase in the time of cutting over the conventional completing method.

A further object of the invention is to provide a combined roughing and finishing tool'for cutting gears in a reciprocatory planing operation which has separate roughing and finish-cutting parts'that are arranged to operate successively on a gear blank as the tool isreciprocated across the face of the blank.

Another object of the inventionis to provide a combined roughing and finishingplaning tool'in which both the roughing and finishing parts may be sharpened with 'frontrake' so as to obtain very keen cutting action. 7 -f Still another object of the invention is toprovide a combined roughing and; finishin 13 8,11,:

ingtool which. is so. constructed that the finish-.i

ing part will cut on one side. only of the tooth space sothat when the finishing cut" is being taken, there will be noother outtingthrusts on, of the. finishing the tool to disturb the accuracy operation. ,7 7 Other objects of the invention will beiapparent hereinafter from the specification and from the. recital of the appended claims. The present application is intended to cover specifically the novel cutting .method of the present invention andis a. division of my copending application, Serial No. 405,064, filed August 1,1941, in which the new tool is covered specifically.

For completing gears by the method of the present invention, a pair of reciprocato-ry plan ing tools are employed. Each tool has a roughing part and a finishing part, and the roughing part is arranged in advance ofthe finishingpart in the direction of reciprocationof-the tool; In the \preferred construction, the roughing part is sharpened to but on one side of a tooth space and the finishing-partfof a tool is sharpened to cut on the opposite-side or that tooth space. In the preferredconstruction, the finishing'part is made to a greater aetual height' than the roughing part but its actual height is so selected with reference to the height of the roughing part that when the tool is tipped to the top clearance angle required-"forcutting, that is, when the tool is in actual cutting position, the finishing part will not project into the tooth space as far as the roughing part of the tool. Thus the roughing-part of the tool 'will relieve the tipof the'finishing part of the tool of all or of practically all cutting, and the finishing part will cut substantially on the side of a toothspacei only. The process of the presentinvention may be employed for cutting gears in either a generating or a form-cutting operation. For form-- cutting straight bevel gears, the'tools arereciprocated across the face of the gear blankin longitudinal-1y converging'paths, while a depthwise feed movement between the tools and blank is efiected until full depth position is reached. In the generating'operation; there'is a generating roll effected 'jbetweentheftoolxand blank during the reciprocation of thetools; the tools may I be fed into depth before the'generating roll be gins or the depthwise feed may be effecteddur-v ing the'first part of the generating roll. In both the form-cutting and igenerating-processes, the tools are, withdrawn and th e blank indexed after each tooth space has been.cut,and whenfthe' blank has been indexed through "a revolution, the geariscomplete. f1 f As' already stated, --t;l 1e tools are'preierably sharpened so that the roughmg and finishing parts of a-tool will operate on opposite sides -of a tooth space of the blank. Preferably the two theblocks with the tool slides l2 and I 3, respectively. 'The tool arms 14 and I5 are adjustable angularly in accordance with the angle of longitudinal convergence of opposite sides of the teeth of the gear to be cut. Each tool cuts on the stroke of its slide in one direction and is out of edges of the two tools, in other, words, are preferably arranged to out on opposite sides of the same tooth. On each cutting stroke of a tool,

the roughing part of the toolengages theblank,

first and takes a cut in the bottom and on one side of a tooth slot. Then the finishing part takes its out on the opposite side of the tooth slot. The two tools are stroked back and forth, cutting'even further into the blank with feed or roll until the tooth space is finished. Then the tools are withdrawn from engagement with the blank, and the blank is indexed. During the cutting of the firsttwo'tooth spaces of the blank, two slots are roughed'out and the adjacent opposite sides of those slots, which bound a tooth, are finished; Thereafter, when the blank is indexed from tooth to tooth, one

tooth slot is roughed and one side thereof finish-cut by one tool while the other tool tapercuts and finishes the opposite side of a tooth slot which has previously been operated on by the first tool. As already stated, when the blank has been indexed through one revolution, the

gear is completed.

- The present invention may be practiced on any standard straight bevel gear cutting machine of the two tool type.

' In the drawings:

-'Fig. 1 is a front elevation of the tool end of a standard type two-tool straight bevel gear generator, showing a pair of planing tools made ac cording to the present invention mounted thereon for practicing this invention;

cutting position on the return stroke of its slide, the pivotal tool boxes I0 and II being swung to and from cutting position at opposite ends of the stroke of their respective slides by the clamping mechanisms of the machine. The tool slides travel simultaneously in opposite directions under actuation of their crank driven reciprocating mechanism. Hence one tool will be cutting on the cutting stroke of its slide while the other tool is in withdrawn position on thereturn stroke of its slide.

One embodiment of tool for practicing the present invention is shown in Figs. 2 and 3. The body portion of this tool is denoted at 25. It is provided with holes 26 through which screws 21 or 28 may be passed to secure the tool to one of the tool boxes II) or II.

The cutting portion of the tool consists of three parts designated as, 30, 3| and 32, respectively. 3!! and 32 are rough-cutting parts, and 3| is a finish-cutting part. The two roughing parts are providedsimply as a. matter of economy so that a given tool may be used at will on either the upper or lower tool slide of a given gear-cutting machine, as will appear hereinafter. Only one roughing part 30 or 32 is operative in any given position of the tool. r

The roughing parts 30-and 32 are similar. Each is of truncated wedge shape and has plane opposite side surfaces 34 and 35 and a plane tip surface 36. The front face 38 of the part 30 is sharpened with a hook and side rake to provide a side-cutting edge at the juncture of the front face 39 with the side 3 5'and a tip-cutting edge Fig. 2 is a plan view of aplaning tool made according to the present invention;

. Fig. 3 isa fragmentary end elevational view of this tool an on enlarged scale; 7

Fig. 4 is a diagrammatic view on an enlarged scale, showing a pair of the improved type of planing tools in engagement with a ge'ar blank andillustrating the process of the present invention; and U Fig. 51s a fragmentaryplan view and Fig. 6 is a fragmentary elevational view with the. tool shown in section on the line 6-6 of Fig. 5, further illustrating the process of the present invention.

already stated, the process of the present invention may be practiced on any conventional type of two-tool straight bevel gear generator. In Fig. l I have shown the tool end of a machine of the type described in the Gleason et al. Patent No. 1,660,502 of February 28, 1928. The present invention may be practiced on this machine by securing tools T and T, whichare made according to the present invention, to the tool boxes of said machine. These tool boxes are denoted at 10 and M, respectively, inthe accompanying drawings.

The tool boxes are pivotallymou'ntedon tool slides l2 and I3, respectively, and the slides l2 and I3 are mounted for'reciprocationon adjust,- able'tool arms l4 and I5, respectively. The tool slides are reciprocated, as described in the patent mentioned, by a crank driven .mechanism which includes the oscillating plate l6, the blocks I1 and l8 which are slidableun the plate, and

thepins |9 and 2ll,'respectively, whichconnect at thejuncture of the tip face 36 with the'front face 38. Similarly, the rear face 40 of the part 32 is sharpened with a hook and side rake to provide side andtip cutting edges at the junctures of the rear face 40 with one side and the tip of this part 32. The side-cutting edge 4| for the rear part 32 lies at the same side of the blade as the side cutting edge 39 of the front roughing part 30.

The finishing part is separated from the roughing parts 30 and 32 by grooves 41 and 48. It is also of. truncated V-shape, having plane opposite sides 44 and 45 and a plane top surface 46. It has its two end faces 49 and 50 sharpened with hooks and side rakes to provide side-cutting'edges 5| and 52, respectively. 7 V

The front and rear cutting faces 39 and 40 of the roughing parts 3|] and 32, respectively, and the front and rear faces 49 and 5|) of the finishing part 3| permit of using the same tool on either the upper or lower tool slides H) or H by simply reversing the tool end for end. When the tool is positioned on the lower tool slide I3, the sidecutting edge 39 of the roughing part 30 and the side cutting edge 5| of the finishing part 3| are effective. When the tool is positioned on the upper slide l2, the side-cutting edge 4| of the roughing part 32 and the side-cutting edge 52 of the finishing part 3| are effective.

The tool is so made that side-cutting edges and 4| of its roughing-partsare 'ofiset laterally beyond theicorresponding side face 45 of the finish-cutting part'-3|.' Likewise, the'tool is so constructed that the side-cuttingedges 5| and 52 of the'finishing part 3| are ofisetflaterally to the opposite side beyond the corresponding sidefaces 34 of the roughing parts. This construction is illustrated clearly in Fig. 3 where r denotes the width of the roughing part 30 at its tip and f denotes the width of the finishing part 3| at its tip.

The finishing part 3| of a tool projects in height a distance :1 beyond the tops 35 of the roughing parts 30 and 32, but when the tool is arranged in actual cutting position, its tip is inclined to the root plane of the work at an angle equal to the top clearance angle requiredfor good cutting action. Thus, as shown in Fig. 5, the tool T is inclined tothe root surface 55 of the gear G, that is to be cut, at a top clearance angle 0. This angle is ordinarily 12. To relieve the tip of the finishing part of cutting, the distance d (Fig. 3) which the finishing part projects beyond the roughing part, is ordinarily made such that when the tool is in cutting position, the finishing part will not cut as deeply as the roughing part of the tool. This is shown in Fig. 5. As will be seen, while the tip of the roughing part 30, in full depth position, travels in the root plane 55 of the tooth space, the tip of the finishing part 3i travels on a line 56 which is parallel to the root plane but above the root plane. The distance d of projection of the finishing part 31 beyond the roughing part 30 or 32 is equal to the distance 3 (Fig. 2) from the front face of the roughing part to the front face of the finishing part times the tangent of the top clearance angle less ordinarily .002" (two thousandths of an inch). The .002 will usually provide sufficient clearance so that the tip of either the finishing or the roughing part,

is less than the width of the tooth spaces of the gear to be cut at the small ends of said tooth spaces. As will be seen in Figs. 4 and 6, during cutting of the first two tooth spaces of a gear blank, then, the side edge 39 and'the tip edge 35 of the roughing part 30 of the lower tool T and the side-cutting edge 5| of the-finishing part 3| of this tool will cut a tooth slot 60 in the blank which has parallel sides, and which is of less width than the width of a finished tooth space. Further, one side 6| of this tooth space will be finished by the finish-cutting edge 5|. Simultaneously, the side edge 39 and tip edge 35 of the roughing part 32 of the upper tool T and the finish-cutting edge 52 of this tool T will cut a tooth slot 62 which has parallel sides and which is also of less width than a finished tooth space.

This tooth slot 62 is inclined to the slot 60 because the paths of travel of the two tools are inclined to one another. Thus two tooth slots 60 and 62 will be roughed out and the two sides 6! and 53 thereof, which bound the tooth 65 of the gear, will be finished.

After the tooth slots 60 and 62 have been cut to full depth, the tools are withdrawn from the blank and the blank indexed. If the indexing is in the direction of the arrow 66 (Fig. 4) then tooth slot 62 while the tool T will operate in the tooth slot bounded by the dotted lines 61 and 68. Since the tool T travels on a path which is inclined longitudinally to the path of travel of the tool T, the finish cutting edge 5| of the tool T will remove the stock between the roughed side surface 69 of the tooth slot 62 and the finished side 10 thereof, producing the final finished tooth surface l0 and completing the finishing of the tooth slot. Simultaneously the tool T will rough out the tooth slot 1| bounded by the sides 61 and 68' and. will finish the side 68 of this tooth slot. Thus the operation will proceed. During each cutting cycle, the tool T will rough out a slot and finish one side thereof, while the tool T will finish the opposite side of a tooth slot which has previously been operated upon by the tool T. During the last cutting cycle, the finish side- 'cutting edge 52 of the tool T will finish the tooth slot 50 of the blank, removing the stock between the roughed tooth surface 12 and the finished tooth side 13, producing the finished tooth side. Simultaneously the tool '1 will be removing the stock between the roughed side '16 and the finished side surface 11 of the tooth slot 15, which willpreviously have been roughed out and partly finished by the tool T. Thus, when the blank has been indexed through a revolution, the gear will have been completed.

While the invention has been described in connection with a finish-cutting operation, it will be understood that it may also be used for rough-'- cutting, particularly on coarse pitchjobs. In this case, the different sections of the tool will all be roughing parts. A roughing tool so made will cut moresmoothly and more rapidly than conventional planing tools because its cutting edges are sharper since opposite side rake is provided on the successive parts of the tool. In this case, the height of the central section 3! of the tool maybe made such that it will be of the same effective cutting height as that of the front operating section of the tool, or the heights of the two parts may be unequal as in the illustrated embodiment of the invention.

Other modifications and uses of the invention will occur to those skilled in the art. The present 7 application is intended to cover any adaptations,

when the tools are fed back into engagement uses, or embodiments of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the gear art and as may be applied to the essential features hereinbefore set forth and as fall within the scope of the invention or the limits of the appended claims.

Having thus described my claim is:

l. The method of cutting a gear which comprises employing a pair of tools, each of which invention, what I has a roughing part and a finishing part arranged, respectively, one in advance of the other inthe direction of cutting movement of the tool, 7

the roughing part being'formed to have one side offset laterally beyond the corresponding side of th finishing part and the finishing part having its opposite sideofiset laterally beyond the corresponding opposite side of the roughing part,

and each part having a side cutting edge formed at its offset side, positioning said tools in engagenally converging paths, periodically withdrawing the tools from engagement with the blank and indexing the blank, and repeating the operation until all the tooth spaces have been cut.

2. The method of cutting a gear which comprises employing a pair of reciprocatory planing tools, each of which has two cutting parts arranged one behind the other in the direction of cutting movement of the tool, and each of which has its two cutting parts sharpened to have opposite side-cutting edges, respectively, positioning said tools so that their front side-cutting edges will operate, respectively,-on the remotely spaced opposite sides of two tooth spaces of a gear blank and their rear side-cutting edges will operate, respectively, on the adjacent opposite sides of said two tooth spaces, and reciprocating said tools in engagement with the blank.

3. The method of cutting a gear which comprises employing a pair of reciprocatory planing tools, each of which has two cutting parts arranged one behind the other in the direction of reciprocation of the tool and each of which has its two cutting parts sharpened to have opposite side cutting edges, respectively, the effective pointwidth of each tool being less than the width of the tooth spaces of the gear to be cut, positioning said tools so that their front side-cutting edges will operate, respectively, on the remotely spaced opposite sides of two tooth spaces of a gear blank and their rear side-cutting edges will operate, respectively, on the adjacent opposite sides of said two tooth spaces, and reciprocating said tools in engagement with the blank to cut tooth slots in the blank, then withdrawing the tools from engagement with the blank, indexing the blank through the distance of a single tooth space, and repeating the operation until all of the tooth spaces of the blank have been cut.

4. The method of cutting a gear which comprises employing a pair of reciprocatory planing tools, each of which has two cutting parts arranged one behind the other in the direction of reciprocation of the tool, the front cutting part of each tool having a side-cutting edge at one side of the tool and a tip-cutting edge and having a greater effective cutting height than the rear cutting part of the tool, and the rear cutting part of each tool having a side-cutting edge at the opposite side of the tool from the front cutting edge of that tool, positioning said tools so that they will operate in different tooth spaces of a gear blank, and reciprocating said tools in engagement with the blank to cut tooth slots in the blank, then withdrawing the tools from engagement with the blank and indexing the blank,

and then repeating the operation until all of the tooth spaces of the blank have been out.

5. The method of cutting a gear which comprises employing a pair of reciprocatory planing tools, each of which has a rough-cutting part and a finish-cutting part arranged one behind the other in the direction of reciprocation of the tool, the rough-cutting part of each tool having a greater efiective cutting height than the finishcutting part of the tool and having a cutting edge at one side of the tool and a tip-cutting edge, the finish-cutting part of 'each tool having a sidecutting edge at the opposite side of the tool, the effective point width of each tool being less than the width of the tooth spaces of the gear to be the distance of a single tooth space, and repeat-- ing the operation until all of the tooth sides of the blank have been finished.

6. The method of cutting a bevel gear which comprises employing apair of reciprocatory planing tools, each of which has two cutting parts arranged one behind the other in the direction of reciprocation of the tool, the two cutting parts of each tool being of generally prismatic shape and having opposite side-cutting edges, respectively, and the effective point-width of each tool being less than the finished width of the tooth spaces -of the gear to be cut, positioning said tools in engagement with a gear blank so that they operate in different tooth spaces of the blank, respectively, reciprocating said tools along longitudinally converging paths, withdrawing the tools from engagement with the blank after a pair of tooth spaces have been cut, and indexing th blank through a single tooth space, and repeating the operation until all of the tooth spaces have been cut.

7. The method of cutting a gear which comprises employing a pair of reciprocatory planing tools, each of which has two cutting parts arranged one behind the other in the direction of cutting movement of the tool, the rear cutting part of each tool being of greater actual height than the front cutting part thereof, and the rear cutting part of each tool having a side cutting edge at one side, at least, which projects beyond the corresponding side of the front cutting part, positioning said tools in engagement with a gear blank so that they will operate, respectively, in two different tooth spaces of the blank and are tilted with respect to the bottoms of said tooth spaces at the required top clearance angle and so that the front cutting part of each tool cuts deeper into the blank, reciprocating said tools in engagement with the blank, and periodically Withdrawing the toolsfrom engagement with the blank and indexing the blank.

8. The method of cutting a gear which comprises employing a pair of reciprocatory planing tools, each of which has two cutting parts arranged one behind the other in the direction of cutting movement of the tool, the rear cutting part of each tool being ofv greater actual height than the front cutting part thereof, and the rear cutting part of each too-l having a side cutting edge at one side, at least, which projects beyond the corresponding side of the front cutting part, positioning said tools in engagement with a gear blank 50 that they are tilted at the required top clearance angle and the front cutting part will cut deeper into the work and the finish cutting parts of the two tools will operate, respectively,

on opposite sides of a tooth of the blank, reciproeating said tools in engagement with the blank, and periodically withdrawing the tools from engagement with the blank, and indexing the blank.

LEONARD Q., CARLSEN. 

